1. Field of the Invention
The present invention relates to apparatus for removing bubbles of gas from a liquid in general, and to apparatus for removing such gas from a process liquid, in particular.
2. Description of the Prior Art
The presence of gas bubbles in a liquid often produces a number of thermal, optical, flow, etc. problems in a variety of situations and/or industries. In the photographic industry, for example, the presence of bubbles whose size equal or exceed the range of bubble sizes between 20-100 microns in certain photographic film coatings reduces film quality to an unacceptable level by causing spots to appear in the finished photographic print. An excessive number of bubbles in such coatings will result in increased film production costs due to the attendant loss in production of acceptable quality film.
Previous attempts at removing bubbles of gas from a liquid have met with varying degrees of success. In U.S. Pat. No. 3,775,947 to DUPONT, et al., gas bubbles are removed from the cooling liquid of an internal combustion engine by passing the liquid through a mass of material or baffle such as synthetic foam, synthetic fibres or the like, in a generally horizontal direction, to reduce the velocity of gas bubbles within the liquid so that the bubbles have time to rise to an overhead venting chamber, and then directing the cooling liquid downward upon exiting from the baffle. While this particular gas bubble removing apparatus may be effective for removing relatively large millimeter size gas bubbles from a flowing liquid, a size suggested by the cavity size of the baffle material recited in the DUPONT, et al. patent, such an arrangement is relatively ineffective for removing relatively small, product quality reducing, micron size gas bubbles from a process liquid due, in part, to the fact that the liquid flow rate near the vent of the gas bubble removing apparatus is not slow enough to allow time for the small bubbles to rise to the gas bubble vent.
In U.S. Pat. No. 2,823,804 to MYRING, air bubbles, as well as other impurities, are removed from petroleum distillates by passing the distillate through a filter in a generally horizontal direction and then directing the distillate downward, as buoyancy forces move the air bubbles upward into an air venting chamber. This arrangement may be effective for removing a sufficient quantity of air bubbles from a petroleum distillate so that it can be used for some particular purpose, but many of the smaller air bubbles passing through the filter would also move downward with the filtered liquid because of the ineffectiveness of the buoyancy forces to prevent such movement, which would make liquid that had been filtered in this manner having the so retained air bubbles unacceptable as a process liquid in many process liquid applications.
Other gas bubble removing prior art devices have disadvantages similar to those mentioned above in that either they are incapable of removing bubbles that are smaller than a certain bubble size, or they are inefficient at removing bubbles having a bubble size that is unacceptable when contained in a process liquid. In addition, some prior art gas bubble removing apparatus introduce unacceptable changes in the volume or flow rate of liquid passing through the apparatus during the gas bubble removal process. Volume or flow rate changes can cause premature release of trapped small diameter bubbles that remain in the flow stream and may have a deleterious effect on a finished product utilizing liquid from the flow stream.